The present invention relates to a method for recording still pictures on a disk which is limited in recording frequency, and also to an apparatus for recording and reproducing still pictures on and from a disk by using the disk as a recording medium.
Tapes which have heretofore been used as a picture recording medium have been superseded by picture recording and reproducing apparatus for recording and reproducing picture signals using writable disks to record or reproduce picture signals, which apparatus have begun to appear on the market. Disks to be used are, for example, hard disks and optical disks, such as MO (magneto-optical disk) and DVD-RAM (digital versatile disk-random access memory).
Among the features of the disks, the one that deserves the first mention is rapid accessibility. Without the need of rewinding as in a tape, any region can be rapidly accessed by simply moving the head over the disk, a great merit from the viewpoint of retrieval.
Another feature is that the disk is suitable for recording still pictures. To record or reproduce still pictures, it is necessary to continue scanning the same recording track on the recording medium, but the tape medium is unsuitable for such operation. In this respect, a non-contact recording medium, such as an optical disk, is of particular merit. The reason is that in the case of the tape medium, the tape contacts the head, failing to endure a prolonged tracking operation.
Fully utilizing the two features of the disk, i.e., the suitability for still picture recording and the rapid accessibility, the apparatus for recording and reproducing still pictures on and from the disk has begun to be widely used in various fields, for picture filing in the medical field and for data preservation in the field of scientific research.
Consider the differences between the tape medium and the disk medium as to the manner of repetitive recording operation in which after one recording has ended, another is effected and so on. In the case of the tape medium, when recording is to be resumed after the end of the preceding recording has ended, the operation may be directly started. Since the physical structure of the tape medium is such that the preceding last recording position can be physically retained even if the recording operation is interrupted by turning off the power or taking out the tape, the subsequent recording can be made on the tape by simply starting to record, without any trouble.
In the case of the disk medium, however, if the recording head remains stopped at the preceding last recording position, it is possible to resume recording from said position. However, once the power has been turned off or the disk has been taken out, the last recording position does not physically remain where it was, getting lost, so that it is impossible to resume recording from the position at which the preceding recording has ended.
Therefore, in disk machines and instruments, it is necessary to somehow know the last recording position in the preceding recording operation before fresh recording. In conventional disk machines and instruments, when the power is turned on or the disk is inserted, the recorded region of the disk is retrieved by making a check on the presence or absence of recorded data so as to retrieve the last recording position; in this way, the process for managing the last recording position has been performed.
Further, a method would be contemplated of writing the last recording position on the disk itself at all times. This method, however, has not been realized. The reason is that as it becomes a problem particularly with optical disks limited in recording frequency, once a picture is recorded, the last position information stored in the disk has to be rewritten, whereby the writing frequency of the recording position information writing region materially increases; thus, the limit of the recording frequency will soon be exceeded. Particularly when still pictures are to be recorded, since the recording position information has to be updated for each still picture, the limit of the recording frequency will soon be exceeded. Therefore, a procedure has been adopted in which the last recording position information is not written on the disk and instead a memory which is not limited in recording frequency is used so that the last recording position information may be written in the memory installed in disk machines and instruments, thereby avoiding this problem.
However, the arrangement of conventional disk machines and instruments presents the following problems.
A problem associated with a method of retrieving the recording region in the disk as when the power is turned on is that a large amount of time is expended for retrieval.
Further, a method of storing the last recording position information in the memory installed in conventional disk machines and instruments, though useful for machines and instruments which use an unremovable medium, such as a hard disk, is not suitable for machines and instruments which allow exchange of disks, such as optical disks. Furthermore, in this case, the disk and the internal memory which records the recording position information corresponding thereto independently exist in separate places. Therefore, the disappearance of the memory information caused as by the power being cut off causes the loss of the relation of one-to-one correspondence between the disk and the machine or instrument and hence the loss of the last recording position information, a situation which could lead to erroneously erasing the pictures recorded on the disk, which is a fatal problem.
The present invention has for its object the provision of a method for recording still pictures on a disk, which shortens the period of time for retrieving a region where a picture is recorded in a disk limited in recording frequency and which improves the recording frequency and ensures a reliable recording operation.
To achieve this object, the invention provides a method for recording still pictures on a disks wherein in recording still pictures on a disk limited in recording frequency, the method comprises the steps of forming said disk with a still picture recording region for recording still pictures, a plurality of recording position information sectors in which recording position information indicating the position of a still picture to be recorded on the disk is recorded, and a pointer sector which specifies a recording position information sector having the last recording position information written therein, when it is desired to record a still picture, recording it in a particular position in said still picture recording region according to the last recording position information written in a recording position information sector specified by said pointer sector, managing said plurality of recording position information sectors so as to prevent the recording frequency of a recording position information sector from exceeding the maximum recording frequency, updating the recording position information about said still picture and the recording frequency of said recording position information sector and recording them in the same or different recording position information sector, and, when the recording position information is recorded in said different recording position information sector, updating said pointer sector on the information which specifies this recording position information sector.
According to the above arrangement, the time for retrieval of a still picture recording region of a disk limited in recording frequency is shortened, the recording frequency of the disk is improved to the greatest degree, and a reliable recording operation is ensured.
Further, another method for recording still pictures on a disk according to the invention, different from the one described above, is a method wherein in recording still pictures on a disk limited in recording frequency, the method comprises the steps of forming said disk with a still picture recording region for recording still pictures, a plurality of recording position information blocks in which recording position information indicating the position of a still picture to be recorded on the disk is recorded in a particular one of a predetermined number of sectors, and a pointer block whereby information which specifies a recording position information block having the last recording position information written therein is recorded in a particular one of a predetermined number of sectors, when it is desired to record a still picture, recording in a particular position in said still picture recording region according to the last recording position information written in a particular sector of a recording position information block specified by said pointer block, managing said plurality of recording position information blocks so as to prevent the recording frequency of a recording position information block from exceeding the maximum recording frequency, updating the recording position information about said still picture and the recording frequency of said recording position information block and recording them in a sector of the same or different recording position information block, and, when the recording position information is recorded in said different recording position information block, updating said pointer sector on the information which specifies this recording position information block.
According to the above arrangement, with a disk such as a DVD-RAM which is limited in recording frequency and adapted to read and write data on a sector basis, such as information on still pictures or recording positions, on the basis of a block consisting of a predetermined number of sectors, it is possible to shorten the time for retrieval of a still picture recording region, to improve the recording frequency of the disk to the greatest degree, and to ensure a reliable recording operation.
The invention provides an apparatus for recording and reproducing still pictures on and from a disk by using a disk limited in recording frequency as a recording medium, said apparatus comprising a still picture recording and reproducing means for recording a still picture in a particular position of a still picture recording region according to the last recording position information recorded in a recording position information sector specified by a pointer sector read out from the disk, and a still picture recording position information recording and reproducing means which, while managing a plurality of recording position information sectors so as to prevent the recording frequency of a recording position information sector from exceeding the maximum recording frequency, updates the recording position information about said still picture and the recording frequency of said recording position information sector and records them in the same or different recording position information sector, and which, when the recording position information is recorded in said different recording position information sector, updates said pointer sector on the information which specifies this recording position information sector.
According to the above arrangement, recording position information can be distributively recorded in a plurality of recording position information sectors, in consideration of the limitation of the recording frequency of the disk, and the last recording position can be reliably recorded on the disk while preventing a breakdown of the recording position information sectors.
Further, in the case where said still picture recording position recording and reproducing means is arranged such that let the maximum number of still pictures recordable on the disk be L (which is a positive integer), the recording limit frequency of the disk be M (which is a positive integer), and the maximum recording frequency of a single recording position information sector be N (which is an integer between 1 and M), and let the total number Q of recording position information sectors be a value calculated from the equation Qxe2x89xa7(Nxc3x97L/M), then, if the total number Q is a number containing a decimal point, the number is rounded up to the nearest integer and an integer equal to or greater than said nearest integer is used as the value of Q. In this case, the last recording position information can be recorded in an optimum manner, so that a breakdown of records can be prevented until all recording position information sectors reach the maximum recording frequency, ensuring that the last recording position is reliably recorded.
Further, in the case where said still picture recording position recording and reproducing means is arranged such that a group of recording position information sectors and a pointer sector are formed between a first still picture recording region formed on the inner peripheral side of the disk and a second still picture recording region formed on the outer peripheral side of the disk and equidistantly or substantially equidistantly from the outer and inner peripheral ends of the disk. In this case, increase of the average seek time for the head of the disk drive is prevented and the time to be taken for the recording of a still picture and the recording of recording position information can be minimized throughout the disk.
Further, the invention provides another apparatus for recording and reproducing still pictures on and from a disk by using a disk limited in recording frequency, different from the one described above, said apparatus comprising an input/output processing means for recording and reproducing data on a sector basis, such as a still picture or recording position information, on said disk on the basis of a block which consists of a predetermined number of sectors, a still picture recording and reproducing means which, when recording a still picture, instructs said input/output processing means to record a still picture in a particular position of the still picture recording region specified by a particular sector of the pointer block read out from the disk, and a still picture recording position information recording and reproducing means which, while managing a plurality of recording position information blocks so as to prevent the recording frequency of a recording position information block from exceeding the maximum recording frequency, instructs said input/output processing means to update the recording position information about said still picture and the recording frequency of said recording position information block and to record them in a sector of the same or different recording position information block, and which, when the recording position information is recorded in said different recording position information block, instructs said input/output processing means to update said pointer block on the information which specifies this recording position information block.
According to this arrangement, even with a disk such as a DVD-ROM adapted for reading and writing data on a sector basis, such as information on still pictures or recording positions, on the basis of a block consisting of a predetermined sectors, it is possible to distributively record recording position information in a plurality of recording position information blocks, and to reliably record last recording position information on the disk, while preventing a breakdown of the records in the recording position information blocks.
Further, in the case where said still picture recording position recording and reproducing means is arranged such that let the maximum number of still pictures recordable on the disk be L (which is a positive integer), the recording limit frequency of the disk be M (which is a positive integer), and the maximum recording frequency of a single recording position information block be N (which is an integer between 1 and M), and let the total number Q of recording position information blocks be a value calculated on the basis of the equation Qxe2x89xa7(Nxc3x97L/M), then if the total number Q is a number containing a decimal point, the number is rounded up to the nearest integer and an integer equal to or greater than said nearest integer is used as the value of Q. In this case, the last recording position information can be recorded in an optimum manner and occurrence of a breakdown of records can be prevented until all recording position information blocks reach the maximum recording frequency, ensuring reliable recording of the last recording position information.
Further, in the case where the input/output processing means is arranged to record and reproduce data, such as a still picture or recording position information, on and from the disk on an ECC block basis. In this case, even if a disk adapted for recording on an ECC block basis, such as a DVD-RAM, is used, the last recording position information can be reliably recorded.
Further, in the case where said still picture recording position recording and reproducing means is arranged such that a pointer block and a group of recording position information blocks are formed between a first still picture recording region formed on the inner peripheral side of the disk and a second still picture recording region formed on the outer peripheral side of the disk and equidistantly or substantially equidistantly from the outer and inner peripheral ends of the disk. In this case, increase of the average seek time for the head of the disk drive is prevented and the time to be taken for the recording of a still picture and the recording of recording position information can be minimized throughout the disk.
In the case where said still picture recording and reproducing apparatus is provided with a use limit frequency setting means which sets a maximum recording frequency for the disk, use limit frequencies may be set according to the performance of disks to be used and user""s desire.